Is there a volcano in your garden? Eruption locations of the Newer Volcanics Province of south-eastern Australia

Did you know there were volcanoes in Victoria? The state is actually home to the Newer Volcanics Province (NVP), a volcanic field stretching 410 km from Melbourne to the Mt. Burr range in South Australia, covering >19,000 km2 and containing >704 eruption points from >416 volcanic centres. The province contains a wide variety of eruption centres, which are both simple and complex in nature, ranging from lava shields and scoria cones to some of the largest maar volcanoes in the world. Explorable caves and lava tubes showcase well-preserved lava flow features, while the province is a fossickers dream, containing abundant mantle xenolith and megacryst collecting localities.

The NVP is the most recent phase of volcanic activity in Australia with an age range of 4.5 million years to ~5000 B. P. at Mt. Gambier, and is still considered active! Local Aboriginal people witnessed some of the eruptions, naming them ‘Willum-a-weenth’ (place of fire).

Eruption locations of the Newer Volcanics Province

The NVP is sub-divided into the Central Highlands, Western Plains and Mt. Gambier sub-provinces based on differences in geomorphology.

The Central Highlands sub-province can be found northwest of Melbourne, containing 54% of NVP volcanic centres.

The Western Plains sub-province extends 320 km from Melbourne to Portland, and contains 42% of NVP volcanic centres.

The Mt. Gambier sub-province is 60 km west of the Western Plains, containing only 4% of eruption centres.

Volcanic centres in the NVP can be split into two groups – simple or complex and then further categorised.

Simple Volcanoes

Simple volcanoes feature few eruption points, dominantly of one form, with simple morphologies (shapes).

Examples of simple volcanoes of the NVP. a) Mt. Elephant scoria cone, b) Picaninny Hill lava shield, c) Lake Keilambete maar. Photos by Julie Boyce and Teagan Blakie.

a)    Scoria cones form by the accumulation of pyroclasts rich in vesicles (holes made by exsolved gases). They can also be associated with outpourings of lava, for example Mt. Elephant, Derrinallum.

b)    Lava shields form from the gradual build-up of fluidal lava flows, which can flow many kilometres. A good example of a lava shield in the NVP is Picaninny Hill, near Penshurst.

c)    Maars form from when magma rising to the surface encounters groundwater. The result is a bowl-shaped crater with a low rim of fine-grained ejecta. Lake Keilambete, between Noorat and Terang is a good example of a simple maar.

Complex Volcanoes

Complex volcanoes feature multiple eruption points and complex morphologies (shapes).

Examples of complex volcanoes of the NVP. d) Mt. Rouse, e) Lake Purrumbete, showing Mt. Porndon in the distance f) Mt. Gambier’s Valley Lake. Photos by Julie Boyce and Jozua van Otterloo.

d)    Magmatic volcanic complexes feature a combination of lava shields, scoria cones and spatter cones. An example is Mt. Rouse, Penshurst, which features eight eruption points of lava and scoria, with lava flows stretching 60 km to the coast at Port Fairy.

e)    Maar volcanic complexes feature multiple eruption points of phreatomagmatic eruption products (e.g. multiple coalesced maars). Lake Purrumbete, Colac is such a volcanic centre. This large 3 km diameter maar was formed by the coalescence of at least three shallow craters during violent eruptions when water interacted with the magma to create explosions of volcanic ash and gas.

f)    Maar-cone volcanic complexes feature a combination of magmatic and phreatomagmatic eruption products, as the magma interacts with water, such as maars, scoria cones and lava flows, like Mt. Gambier. This volcanic centre has more than 14 eruption points of maars, scoria and spatter cones, tuff cones, lavas and pyroclastic flows.

The NVP is considered an active province, with the occurrence of mantle-derived carbon dioxide at locations such as Mt. Gambier. Researchers agree that further eruptions are possible, and eruption frequency has been estimated at between 1:10,800 and 1:12,500 years. A new volcano would be produced with very little warning, perhaps a few small earthquakes. If mantle xenolith predictions are correct, and the magmas can travel tens of metres per second, a magma originating at a depth of 80 km could reach the surface in as little as 2 hours. The hazards encountered would depend on the kind of eruption centre being formed. Hazards would range from small or large-scale lava flows, scoria cone formation, or the eruption of a maar volcano with resultant ash plumes. Don’t worry; chances are high you would be able to escape an eruption. Will the Newer Volcanics Province erupt again? We don’t have enough information to be able to predict an eruption, so the truth is we don’t actually know!

Why not see if there is a volcano in your garden! A Google Earth kml file is available showing all eruption points for the Newer Volcanics Province, and central locations for complex eruptions. The file can be downloaded here, and is best viewed with a vertical exaggeration of 3 as many of the lava shields have very low relief. This can be changed in preferences of Google Earth. Don’t forget to drag the folder out of ‘Temporary Places’ and into ‘My Places’ to save. Alternatively you are able to view it by clicking 'here'

This web page contains information from the following articles:

BOYCE, J.A. 2013. The Newer Volcanics Province of southeastern Australia: a new classification scheme and distribution map for eruption centres. Australian Journal of Earth Sciences: An International Geoscience Journal of the Geological Society of Australia, 60:4, 449-462, DOI: 10.1080/08120099.2013.806954.

BOYCE, J., NICHOLLS, I., KEAYS, R. & HAYMAN, P. 2013. Victoria erupts. The Newer Volcanics Province of south-eastern Australia. Geology Today (in press).

JORDAN, S. C., CAS, R. A. F. & HAYMAN, P. C. 2013. The origin of a large (>3 km) maar volcano by coalescence of multiple shallow craters: Lake Purrumbete maar, southeastern Australia. Journal of Volcanology and Geothermal Research 254, 5–22.

VAN OTTERLOO, J., CAS, R. A. F. & SHEARD, M. J. 2013. Eruption processes and deposit characteristics at the monogenetic Mt. Gambier Volcanic Complex, S. E. Australia: implications for alternating magmatic and phreatomagmatic activity. Bulletin of Volcanology, special collection on Monogenetic Volcanism (in press).

A full database of eruption points, including shapefiles for ArcGIS, for scientific use, can be obtained from http://www.researchgate.net/profile/Julie_Boyce/publications  

For further information, please contact Julie Boyce.

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